Electroejaculation and semen evaluation in olive ridley turtle (Lepidochelys olivacea) and hawksbill turtle (Eretmochelys imbricata) in Thailand

Abstract

Electroejaculation and semen evaluation were successfully performed on the olive ridley turtles (Lepidochelys olivacea) and hawksbill turtles (Eretmochelys imbricata) at Phuket Marine Biological Center (PMBC), Phuket province and Eastern Marine and Coastal Resources Research Center (EMCOR) Rayong province, in Thailand. Six male Olive Ridley turtles aged approximately 30 years old and weighing between 28.0 – 35.4 kilograms and 3 male Hawksbill turtles aged approximately 16 years old and weighing between 40.0-49.0 kilograms were used. The study on the Olive Ridley turtle was performed in May (Summer season) and on the Hawksbill turtle was performed in October (Rainy season). Before electroejaculation, each turtle was sedated and an electrical rectal probe was applied into its cloaca and stimulated with 2-6 volts electrical stimuli in 4 cycles. After electrical stimulation, manual stimulation was continued for complete penile erection. The results of semen evaluation found that, an average semen volume was 1 ml (range 0.01 to 2.2 ml) for Olive Ridley turtle (n=6), and 4.4 ml for Hawksbill turtle (n=1). Seminal fluid had turbidity, opalescence, viscosity and mucoid appearance. An average sperm motility was 28.25 % (range 0 to 98 %) for Olive Ridley turtle, and 60 % for Hawksbill turtle. An average sperm concentration was 67.3 million/ml (range 11.5 to 150 million/ml) for Olive Ridley turtle, and 512 million/ml for Hawksbill turtle. The sperm had narrow heads and moved in a spiral movement. There were also some motile lobulated appearances in seminal fluid which were of unknown function. Sperm viability in external milieu was approximately 90 minutes. Several staining agents used in the study were not suitable for sperm morphology evaluation. In conclusion, this study was the first report of successful semen collection using electroejaculation in olive ridley and hawksbill turtles in Thailand. The semen collection method developed here is a useful technique for an artificial insemination in order to conserve the threatened and endangered sea turtle species in the future.